Field of the Invention
The present invention relates to an image reading apparatus that is provided with an original conveyance device and an image reading apparatus body, and an image forming apparatus equipped with the image reading apparatus concerned. Particularly, the present invention relates to the image reading apparatus that is capable of determining an opening-closing state of the original conveyance device that is pivotally mounted on an upper portion of the image reading apparatus body, and the image forming apparatus equipped with the image reading apparatus concerned.
Description of the Related Art
In an image reading apparatus equipped with an original conveyance device (an automatic document feeder, hereinafter, referred to as an “ADF”), the ADF is mounted on a reading apparatus body that reads an original. One side of an under face of the ADF is pivotally attached to one side of an upper face of the reading apparatus body through a hinge member. Accordingly, the ADF is pivotable upon the hinge member as a pivot. When the ADF is closed and covers a platen, which is the upper face of the reading apparatus body, a pressure plate at the under face of the ADF presses an original placed on the platen, the image reading apparatus will be ready to read.
An image forming apparatus equipped with an ADF that exposes and covers a platen of a reading apparatus body is usually provided with a flag-type opening-closing detection sensor for detecting opening and closing of the ADF. The flag-type opening-closing detection sensor has a projection member and is arranged near a hinge member. When the ADF opens, the projection member is projected and the sensor detects opening of the ADF. When the ADF is closed, the projection member is pressed by the under face of the ADF and the sensor detects closing of the ADF.
However, the flag-type opening-closing detection sensor merely determines whether the opening angle of the ADF is larger than a predetermined angle. Accordingly, even if a thick original is placed on the platen and a pressure plate at the under face of the ADF (hereinafter referred to as the “ADF”, simply) is floated slightly from the platen, the flag-type opening-closing detection sensor determines that the ADF is closed. Then, when a moving original is read with the ADF in the state where the ADF is floated slightly, paper jam occurs due to the floating of the ADF, at least one of the original in the ADF and the original on the platen may be damaged.
Against this, for example, Japanese Laid-Open Patent Publications (Kokai) No. 2014-011766 (JP 2014-011766A), No. 2006-025284 (JP 2006-025284A), and No. 2010-278563 (JP 2010-278563A) disclose techniques that detect the state where the ADF is floated slightly that cannot be detected by the flag-type opening-closing detection sensor. The techniques move a movable image reader to a moving-original-reading position or to a position under a platen glass, read a pressure plate or an ADF counter member, and detect the opening/closing state of the ADF on the basis of the obtained luminance value or the size relation of the reading sizes of two white marks attached to front and rear sides of the ADF.
However, when the opening/closing state of the ADF is detected by reading the pressure plate or the ADF counter member using the movable image reader, it is necessary to move the image reader from a standby position to the moving-original-reading position or to the position under the platen glass. Accordingly, the time during which the image reader moves to the moving-original-reading position is needed.